The present invention relates to a method of aerobic cultivation of yeasts, and more particularly to such a method wherein high cell concentration is employed during cultivation.
In the prior art, unsuccessful attempts have been made to enhance cell concentration in an aerobic cultivation method. These attempts have principally focused on nutrient supply control and oxygen supply control. The latter methods involved development of a fermentor which improved the speed of oxygen supply, a method using oxygen as proposed in Japanese Pat. No. 9833/1976 and the like. However, all of the prior methods were found deficient in one way or another, and did not successfully enhance cell concentration.
In analyzing the failure of the previous methods, it appears that a number of factors prohibit or retard multiplication of yeast cells in an aerobic cultivation; such as (1) shortage of a main carbon source, inorganic salts or other nutrients; (2) shortage of oxygen; (3) accumulation of metabolites of yeasts; and (4) accumulation of salts. Thus, eliminating the first two factors, namely, (1) and (2), would still not satisfactorily improve cell multiplication and cell concentration, since cultivation is suppressed by the other factors (3) and (4) mentioned above.